[WIP, DONT REVIEW] add initializer to graph proto

[jslhcl]

Description

Motivation and Context

[chilo-ms]

If we want to construct the model proto via manipulating the graph proto directly, and then serialize model proto to string/array for (1) onnx-tensorrt parser to consume and (2) ORT TRT to deserialize it when calling OrtGraph_DeserializeFromArray to get the ORT graph.

Then it's not binary compatible (you already mentioned before) is the concern.

The reason is EP shared lib might use one version of protobuf to serialize the model proto to array/string, and ORT uses another version of protobuf to deserialize it. And we know that proto serialization is not stable per doc.

But we can probably do what Adrian previously mentioned that ORT provides an API to tell EP developer which protobuf version it uses to make sure EP share lib can link against the same protobuf lib.